Hidden benefits of Australia's coastline: seawater power

In an Australian first, a feasibility study into a seawater-pumped hydro project in South Australia’s Spencer Gulf has found it could generate up to 225 megawatts of renewable energy, with a storage capacity of 1770 megawatt hours – more than 13 times the capacity of Tesla’s South Australian battery system, 200 kilometres away.

The Spencer Gulf coastline, where the Seawater Pumped Hydro project has been trialled. Photo: V.Menkov

As this potential becomes increasingly apparent the focus is shifting from freshwater sources to utilising Australia’s coastline for power.

However, costs are higher compared to freshwater pumped hydro systems, with estimated capital costs forecast at about $2.1 million per megawatt of installed capacity., with operating costs of between $11 million and $12 million per year. Initial estimates forecast the power plant at Cultana in the Spencer Gulf would cost $477 million to build, and have a potential operational life of up to 30 years.

The study found the plant could go from standstill to full output within 90 seconds on a single unit, and to full load on the entire station within 150 seconds.

Federal Energy Minister Josh Frydenberg said the report was encouraging for further work on saltwater pumped hydro.

«The study shows that the Cultana project is technically feasible, can address the market need for energy firming to facilitate the growth of renewable energy in South Australia and is economically viable under a range of plausible scenarios,» he said.

Get the latest news and updates emailed straight to your inbox.

The study was carried out by a consortium comprising EnergyAustralia, Arup and the Melbourne Energy Institute, and funded in part by the Australian Renewable Energy Agency (ARENA).

The pumped hydro system draws upon seawater, rather than freshwater reservoirs. Photo: ARENA

It investigated the use of seawater-pumped hydro due to the lack of freshwater sources in South Australia.

«The sewater-pumped hydro storage technology could be deployed widely across Australia,» the ARENA report stated, «especially where freshwater resources are limited, to support the growing share of renewable energy in the generation mix.»

«A major advantage of seawater-pumped hydro energy storage is an abundant water supply in arid and semi-arid regions and no need for a lower reservoir.»

Unlike freshwater-pumped hydro energy systems, such as the Snowy Hydro, seawater systems have historically faced the issue of corrosion, operating in marine environments, and ‘biofouling’, which can limit the in-flows of water.

Currently, there has only been one operational seawater-pumped hydro plant in the world, the 30 megawatt Yanbaru Power Station, on Okinawa Island in Japan. It ran from 1999, after four years of testing, until it was decommissioned in 2016.